Bobbin gear drive for roving frames

ABSTRACT

A bobbin gear drive means for a textile roving frame has a bobbin gear unit including a sleeve loosely mounted on each bolster shaft for supporting a bobbin thereon, and a tubular bobbin spur gear, made from a plastic material, such as nylon, is mounted on each sleeve so that the teeth thereof may wear away instead of the teeth of the usual spiral face gear meshing in hypoid relationship therewith. Thus, the spiral face gears rarely have to be replaced, and it is a relatively simple matter to replace the tubular bobbin gear. Also, the teeth of each bobbin gear are relatively long so that, upon a portion of the bobbin gear becoming worn excessively by engagement with a corresponding spiral face gear, the bobbin gear can be turned end-for-end on the sleeve to present a non-worn portion thereof for engagement with the corresponding spiral face gear.

United States Patent [1 1 Lawson [451 July 31,1973

[75] Inventor: Lonnie Gravely Lawson, Lawson,

[73] Assignee: Fieldcrest Mills, Inc., Eden, N.C.

[22] Filed: Feb. 22, 1972 [21} Appl. No.2 228,051

Primary ExaminerJohn Petrakcs AttorneyDonald M. Seltzer et al.

[57] ABSTRACT A bobbin gear drive means for a textile roving frame has a bobbin gear unit including a sleeve loosely mounted on each bolster shaft for supporting a bobbin thereon, and a tubular bobbin spur gear, made from a plastic material, such as nylon, is mounted on each sleeve so that the teeth thereof may wear away instead of the teeth of the usual spiral face gear meshing in hypoid relationship therewith. Thus, the spiral face gears rarely have to be replaced, and it is a relatively simple matter to replace the tubular bobbin gear. Also, the teeth of each bobbin gear are relatively long so that, upon a portion of the bobbin gear becoming worn excessively by engagement with a corresponding spiral face gear, the bobbin gear can be turned cnd-for-end on the sleeve to present a non-worn portion thereof for engagement with the corresponding spiral face gear.

12 Claims, 3 Drawing Figures BOBBIN GEAR DRIVE FOR ROVING FRAMES This invention relates to an improved drive means for supporting and rotating the bobbins on a roving frame, and more especially, to an improved bobbin gear unit or assembly which greatly increases the useful life of the usual hypoid or spiral face gears of the bobbin drive means and obviates the need for lubricating the spiral face gears.

As is well known, in the conventional bobbin drive gear train of a roving frame, rows of support blocks or bolsters are carried by a vertically reciprocating bolster rail on which horizontally disposed bobbin drive shafts are rotatably mounted. The bobbin drive shafts are provided with relatively large hypoid or spiral face gears adjacent each bolster which mesh with a relatively smaller bobbin spur gear rotatably mounted on the respective bolster. A bobbin is positioned on the upper surface of each bobbin gear and a strand of roving is directed to each bobbin by a rotating flyer. The upper portion of each spur gear is provided with one or more key-like projections which engage corresponding grooves in the base of the bobbins to impart rotation thereto.

Both the spiral face gear and the bobbin spur gear for driving each bobbin are usually made from cast iron and thus require lubrication at a location which is subject to large accumulations of lint. As the lint builds up between the interrneshing gears, there are increasing radial forces between the spiral face gears and the bobbin spur gears which tend to obstruct rotation of the bobbin spur gears and also tend to force the intermeshing gears apart from each other. This frequently results in the teeth being stripped off of both the bobbin spur gears and the spiral face gears thus requiring replacement of the mutilated gears. The replacement of mutilated bobbin spur gears is not a difficult or time consuming task, since it is merely necessary to lift the bobbin spur gears off of the bolster shaft on which they are rotatably mounted. However, in order to replace one or more of the spiral face gears, it is necessary to remove the corresponding bobbin drive shaft, which extends substantially throughout the length of the roving frame, and then remove the particular mutilated spiral face gear and replace the same with a new gear. For example, in the event that one of the spiral face gears near the center of a bobbin drive shaft becomes mutilated or otherwise defective, all of the spiral face gears on the shaft, up to that one which is defective, have to be removed from the bobbin drive shaft and the new gear installed, whereupon the balance of the gears previously removed must be reinstalled on the bobbin drive shaft. This frequently results in a down time of the roving frame of up to six hours or more, with a consequent substantial loss in production.

It is therefore an important object of this invention to provide an improved bobbin gear drive means facilitating the use of conventional cast iron metal spiral face gears, but which substantially eliminates the problem of any of the spiral face gears being stripped or otherwise mutilated in the event of obstruction to rotation of any of the bobbin gears, which also eliminates the necessity for lubricating the bobbin gear drive means, and which renders the changing of the bobbin spur gears a very simple and relatively economical operation, as well as increasing the useful life of the bobbin spur gears.

It is a more specific object of this invention to provide a bobbin gear drive means facilitating the use of conventional cast iron spiral face gears, and comprising a spur gear unit including a sleeve which is rotatable on each bolster shaft and rests upon the bolster support block. A tubular bobbin spur gear is mounted on each sleeve and is formed of a plastic material, preferably nylon, which is self-lubricating and is engaged by the respective spiral face gear for rotating the spur gear unit and the bobbin resting thereon whereby the spur gear teeth will be worn away by the spiral face gears without occurrence of any substantial wear of the teeth of the spiral face gears and, as heretofore stated, it is a simple matter to replace any of the spur gears which may become worn. Also, because of the relatively ductile nature of the plastic material, in the event of any impediment obstructing rotation of the spur gear unit, the teeth of the bobbin spur gear may be deformed or will strip without adversely affecting the teeth on the spiral face gears, with the result that in all probability the spiral face gears will never be damaged to any noticeable extent. Also, since the bobbin spur gear is formed from nylon or other self-lubricating material, it

is unnecessary to lubricate the bobbin gear drive means, thus eliminating the time required heretofore for replacing the spiral face gears and for periodically removing accumulations of lint from a conventional bobbin gear drive means.

It is still another object of this invention to provide improved means for supporting each bobbin on a roving frame and rotating the same from each respective spiral face gear including a sleeve rotatable on each of the bolster shafts and supported on the bolster support block, with a flange on the upper portion of the sleeve providing a seat for receiving the lower end of the respective bobbin thereon. A tubular spur gear of plastic material is slidably mounted on the sleeve and meshes with the respective spiral face gear for rotating the sleeve and thus the bobbin thereon, with connecting means carried by the flange and projecting between the teeth of the spur gear, such connecting means preferably being in the form of one or more shear pins so that either the connecting means or the teeth of the tubular spur gear will be broken or mutilated upon occurrence of an obstruction to rotation of the sleeve to aid in preventing damage to the spiral face gear rotating in engagement therewith. Preferably, the spur gear is of a length substantially greater than that length thereof which is engaged by the respective spiral face gear so that, upon a corresponding portion of the spur gear becoming worn, it is a simple matter to remove the sleeve with the spur gear thereon from the bolster shaft, turn the tubular spur gear end-for-end and resposition the same on the sleeve so as to provide a non-worn portion of the tubular spur gear for engagement by the corresponding spiral face gear. This arrangement also is advantageous in that conventional bobbin gear units, whether or not they may be defective, may be readily modified to form the aforementioned sleeves therefrom simply by machining the conventional bobbin gear units to remove the gear teeth therefrom, whereupon the tubular spur gear may be readily positioned on the thus modified conventional spur gear unit so that the change-over to the use of the tubular spur gears of this invention may be effected relatively economically.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds, when taken in connection with the accompanying drawings, in which FIG. 1 is a vertical sectional view through the bolster rail and spindle rail at one side of a roving frame, illustrating the improved bobbin gear drive means and the gear train arrangement for rotating the flyers of the roving frame;

FIG. 2 is an enlarged fragmentary elevation, partially broken away and partially in section, taken substantially along line 2-2 in FIG. 1, with the lower portion of the corresponding bobbin and the upper portion of the corresponding spiral face gear being shown in phantom lines; and

FIG. 3 is a partially exploded perspective view of one of the bobbin spur gear units removed from the roving frame.

Referring more specifically to the drawings, in which portions of a conventional roving or fly frame are shown, the vertically reciprocable bolster rail is indicated at and the lower, fixed, spindle rail is indicated at 11. The lower ends of substantially vertically disposed rotatable spindles 12, 12a are supported adjacent opposite sides of spindle rail 11 and are rotated by respective spindle drive shafts 13, 13a drivingly connected to the spindles 12, 12a by conventional gear trains 14, 14a.

A plurality of bolsters or support blocks are suitably supported by and spaced in staggered relationship along opposite sides of bolster rail 10, there being only two bolsters 15, 15a shown in FIG. 1. It is apparent, therefore, that there is a row of bolsters extending longitudinally of the roving frame and positioned adjacent each side of bolster rail 10. Spindles 12, 12a extend upwardly and loosely penetrate the respective bolsters 15, 15a and have respective flyers 16, 16a mounted on their upper ends. Since bolsters 15, 15a and associated parts are substantially identical, only bolster 15 and the parts associated therewith will be described in detail and the parts associated with bolster 15a will bear the same reference characters, where applicable, with the letter a added to avoid repetitive description.

Each bolster 15 is provided with an upwardly extend- I ing tubular bolster shaft 20 thereon (FIG. 2) loosely penetrated by the corresponding spindle 12 for loosely receiving thereon a corresponding tubular bobbin 21 which rests upon and is driven by an improved bobbin gear unit to be later described. It is apparent that each bobbin is positioned so as to properly receive a roving strand from the respective flyer 16 during relative rotation of the bobbins and the flyers.

Extending past the row of spindles 12, and offset with respect to the spindles 12, is a conventional bobbin drive shaft 22 which is driven by suitable means, not shown, and is journaled on the corresponding bolster 15. Bobbin drive shaft 22 has a plurality of relatively large metallic hypoid or spiral face gears 24 fixed thereon, which are usually made from cast iron, and which impart rotation to the respective bobbins 21 through the improved bobbin supporting and rotating means to be presently described. I

In a preferred embodiment of the invention, each bobbin supporting and rotating means adjacent shaft 22 comprises a bobbin gear unit broadly designated at 30 and including a vertically disposed metal sleeve 31 which may be made from cast iron. In fact, sleeve 31 may be formed by modifying a conventional cast iron bobbin gear in the manner described earlier herein.

Sleeve 31 is rotatably mounted on bolster shaft 20, preferably by means of a suitable self-lubricating bushing or sleeve bearing 32 of relatively low friction material. The upper portion of sleeve 31 is provided with an enlarged radially extending flange 33 providing a seat for receiving thereon the lower end of the respective bobbin 21. Flange 33 is integral with sleeve 31 and has a reduced upwardly projecting tubular portion 34 integral therewith which snugly receives the lower portion of the corresponding bobbin 21 so as to properly center bobbin 2-1 with respect to bolster shaft 20 and spindle 12. Porjecting radially outwardly from the reduced portion 34 of sleeve 31, and also projecting upwardly from flange 33, is one or more upwardly extending key-like projections 35 adapted to engage corresponding radial key-ways or slots in the base of the corresponding bobbin and serving to transmit rotation from sleeve 31 to bobbin 21.

A driving connection is provided between each sprial face gear 24 and the respective sleeve 31 for rotating the same and the bobbin 21 thereon and includes means responsive to a predetermined excessive opposing torque condition between gear 24 and sleeve 31, as by an obstruction to rotation of sleeve 31, for interrupting or relieving the driving connection therebetween. Accordingly, a bobbin gear in the form of an elongate, tubular spur gear 40 is slidably mounted on sleeve 31 and is of such length with respect to the teeth of the adjacent spiral face gear 24 that no more than about onehalf of the length of the teeth of spur gear 40 is engaged by the teeth of spiral face gear 24. In other words, the uppermost portion of spiral face gear 24 engaging spur gear 40 is positioned below the midpoint of the length of the teeth of spur gear 40.

As shown, spur gear 40 is somewhat shorter than sleeve 31 and may be held against, or in close proximity to, the lower surface of flange 33 by any suitable means such as a snap ring 42 fitting in a suitable peripheral groove 43 provided in a lower portion of sleeve 31. Snap ring 42 is so positioned as to permit spur gear 40 to be rotated by spiral face gear 24 and relative to sleeve 31 in the event of lint or any other impediment obstructing or tending to retard rotation of sleeve 31.

Means is provided for interconnecting spur gear 40 and sleeve 31 so as to rotate sleeve 31 and the bobbin 21 thereon with gear 40. Such interconnecting means preferably is in the form of a plurality of circularly spaced, relatively short, frangible shear pins 45 depending from flange 33 with their lower portions positioned between the upper portions of adjacent teeth of spur gear 40. Preferably, shear pins 45 are made from metal and pressed into suitable holes provided in flange 33.

Also, spur gear 40 is made from such a material as compared to that of spiral gear 24 as to be capable of being mutilated by the shear pins 45 if they fail to break upon occurrence of an obstruction to rotation of sleeve 31. Therefore, spur gear 40 is made from a suitable plastic, preferably nylon (a long-chain polymeric amide).

Thus, it can be seen that, in the event of any impediment obstructing rotation of gear 31 to such an extent as to subject spiral face gear 24 to excessive opposing forces such as might otherwise damage the spiral face gear, the frangible shear pins 45 will break and/or the shear pins will break away the upper portions of the teeth of the plastic tubular spur gear 40 and spur gear 40 then may be rotated, independently of sleeve 31, by spiral face gear 24. In the event of a very sudden occurrence of such an obstruction, the inertial forces thus imposed may cause the spiral face gear 24 to strip or otherwise mutilate a few teeth of the spur gear 40, but in any such event, the probability of the spiral face gear 24 being damaged is quite remote.

Notwithstanding the factors just described contributing to long useful life of the spiral face gear 24, since spur gear 40 is formed of a material of relatively low wear resistance as compared to that of each spiral face gear 24, it is apparent that the teeth of spur gear 40 will wear away without effecting any appreciable wear of the teeth of spiral face gear 24 and, of course, since it is a simple matter to lift bobbin gear unit 30 off of bolster l5 and its bolster shaft 20, spur gear 40 may be replaced much more easily than the spiral face gear 24. Also, it is apparent that it is more economical to manufacture and replace the tubular spur gear 40 than it would be to manufacture and replace a conventional type of cast iron bobbin gear.

Additionally, it is important to note that, since spur gear 40 is relatively long to the extent that only its lower portion below the midpoint of its length meshes with the respective spiral face gear 24 for rotating spur gear 40 with the sleeve 31 and the bobbin 21 mounted thereon, it is apparent that, upon the lower portions of the teeth of spur gear 40 becoming worn excessively, bobbin gear unit 30 may be removed from the bolster and its bolster shaft 20. Then, by removing the snap ring 42 from the groove 43 in sleeve 31, spur gear 40 may be removed from the sleeve, turned end-for-end and reinstalled on sleeve 31 to present a non-worn portion of the spur gear for engagement by the respective spiral face gear 24 when the corresponding bobbin gear unit is again positioned on the bolster 15 to thereby increase the useful life of both the spiral face gear and the spur gear.

In the drawings and specification, there has been set forth a preferred embodiment of the invention and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

That which is claimed is:

l. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective supports blocks; improved means for supporting each bobbin and rotating the same from each respective spiral face gear, said means comprising a sleeve rotatable on each of said bolster shafts and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon, and

a driving connection between at least one of said spiral face gears and the respective sleeve for rotating the same and the respective bobbin thereon and including means responsive to a predetermined excessive opposing torque condition between said one spiral face gear and said respective sleeve, as by an obstruction to rotation of said respective sleeve, for interrupting said driving connection therebetween.

2. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective support blocks; improved means for supporting each bobbin and rotating the same from each respective spiral face gear, said means comprising a sleeve rotatable on each of said bolster shafts and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon,

a tubular spur gear slidably mounted on said sleeve and meshing with the respective spiral face gear for rotating said sleeve and the bobbin thereon, and

frangible means interconnecting said spur gear and said sleeve and being breakable upon occurrence of an undesirable obstruction to rotation of said sleeve whereby said spiral face gear may rotate relative to said sleeve to prevent mutilation of said spiral face gear.

3. A structure according to claim 2, wherein said frangible means comprises at least one shear pin fixedly mounted in and depending from said flange, and having its lower portion positioned between upper portions of adjacent teeth of said spur gear.

4. A structure according to claim 2, wherein said tubular spur gear is formed of plastic.

5. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective support blocks; improved means for supporting at least one of the bobbins and rotating the same from the respective spiral face gear, said means comprising a sleeve rotatable on the respective bolster shaft and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon,

a tubular spur gear slidably mounted on said sleeve and meshing with said respective spiral face gear for rotating said sleeve and the bobbin thereon,

connecting means carried by said flange and projecting downwardly between the teeth of said spur gear, and

said spur gear being made from such a material as compared to that of said spiral face gear as to be capable of being mutilated by said connecting means upon occurrence of an obstruction to rotation of said sleeve to aid in preventing damage to said spiral face gear rotating in engagement with said spur gear.

6. A structure according to claim 5, wherein said spur gear is made from a low friction plastic material to obviate the need for use of a lubricant between said sprial gear and said spur gear.

7. A structure according to claim 5, wherein said spur gear is of an axial length at least about twice that of the portion thereof meshing with said spiral gear, and wherein such meshing portion is located adjacent one end only of said spur gear whereby, upon said meshing portion becoming worn to excess, said spur gear may be removed from said sleeve, turned end-for-end and reinstalled on said sleeve to present a non-worn portion thereof for meshing with said spiral gear.

8. A structure according to claim 5, wherein said connecting means comprises at least one relatively short shear pin projecting from said flange into the space between adjacent teeth of said spur gear and being subject to shear by said teeth in the event that the adjacent end of said spur gear is not mutilated sufficiently by engagement with said shear pin to relieve the stress to which said spiral gear is subjected upon said occurrence of an obstruction to rotation of said sleeve.

9. in a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective support blocks; improved means for supporting each bobbin and rotating the same from each respective spiral face gear, said means comprising a sleeve rotatable on each of said bolster shafts and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon,

an elongate tubular spur gear removably mounted on said sleeve and having a lower portion only thereof below the midpoint of its length meshing with the respective spiral face gear for rotating said spur gear, means interconnecting said spur gear and said sleeve to rotate said sleeve and the bobbin thereon, and

said spur gear being of a material of relatively low wear resistance relative to that of said respective spiral face gear whereby said lower portion of said spur gear may wear away during use without any substantial wearing away of said respective spiral face gear, and whereby said spur gear may be removed from said sleeve, turned end-for-end and reinstalled on said sleeve to present a non-worn portion of said spur gear for engagement by said respective spiral face gear to increase the useful life of both the spur gear and the respective spiral face gear.

10. A structure according to claim 9, wherein said spur gear is made from nylon (long-chain polymeric amide).

11. A structure according to claim 9, wherein said spiral face gear is metal and said spur gear is plastic.

12. A structure according to claim 11, wherein said plastic is nylon, thus obviating the need for a lubricant between said spur gear and said spiral gear. 

1. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective supports blocks; improved means for supporting each bobbin and rotating the same from each respective spiral face gear, said means comprising a sleeve rotatable on each of said bolster shafts and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon, and a driving connection between at least one of said spiral face gears and the respective sleeve for rotating the same and the respective bobbin thereon and including means responsive to a predetermined excessive opposing torque condition between said one spiral face gear and said respective sleeve, as by an obstruction to rotation of said respective sleeve, for interrupting said driving connection therebetween.
 2. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective support blocks; improved means for supporting each bobbin and rotating the same from each respective spiral face gear, said means comprising a sleeve rotatable on each of said bolster shafts and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon, a tubular spur gear slidably mounted on said sleeve and meshing with the respective spiral face gear for rotating said sleeve and the bobbin thereon, and frangible means interconnecting said spur gear and said sleeve and being breakable upon occurrence of an undesirable obstruction to rotation of said sleeve whereby said spiral face gear may rotate relative to said sleeve to prevent mutilation of said spiral face gear.
 3. A structure according to claim 2, wherein said frangible means comprises at least one shear pin fixedly mounted in and depending from said flange, and having its lower portion positioned between upper portions of adjacent teeth of said spur gear.
 4. A structure according to claim 2, wherein said tubular spur gear is formed of plastic.
 5. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective support blocks; improved means for supporting at least one of the bobbins and rotating the same from the respective spiral face gear, said means comprising a sleeve rotatable on the respective bolster shaft and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon, a tubular spur gear slidably mounted on said sleeve and meshing with said respective spiral face gear for rotating said sleeve and the bobbin thereon, connecting means carried by said flange and projecting downwardly between the teeth of said spur gear, and said spur gear being made from such a material as compared to that of said spiral face gear as to be capable of being mutilated by said connecting means upon occurrence of an obstruction to rotation of said sleeve to aid in preventing damage to said spiral face gear rotating in engagement with said spur gear.
 6. A structure according to claim 5, wherein said spur gear is made from a low friction plastic material to obviate the need for use of a lubricant between said sprial gear and said spur gear.
 7. A structure according to claim 5, wherein said spur gear is of an axial length at least about twice that of the portion thereof meshing with said spiral gear, and wherein such meshing portion is located adjacent one end only of said spur gear whereby, upon said meshing portion becoming worn to excess, said spur gear may be removed from said sleeve, turned end-for-end and reinstalled on said sleeve to present a non-worn portion thereof for meshing with said spiral gear.
 8. A structure according to claim 5, wherein said connecting means comprises at least one relatively short shear pin projecting from said flange into the space between adjacent teeth of said spur gear and being subject to shear by said teeth in the event that the adjacent end of said spur gear is not mutilated sufficiently by engagement with said shear pin to relieve the stress to which said spiral gear is subjected upon said occurrence of an obstruction to rotation of said sleeve.
 9. In a roving frame for winding strands of textile roving on bobbins and including a row of support blocks having respective upright bolster shafts thereon, and a driven substantially horizontal bobbin shaft adjacent said support blocks and having spiral face gears located thereon adjacent respective support blocks; improved means for supporting each bobbin and rotating the same from each respective spiral face gear, said means comprising a sleeve rotatable on each of said bolster shafts and supported on the respective block, a flange on an upper portion of said sleeve providing a seat for receiving the lower end of the respective bobbin thereon, an elongate tubular spur gear removably mounted on said sleeve and having a lower portion only thereof below the midpoint of its length meshing with the respective spiral face gear for rotating said spur gear, means interconnecting said spur gear and said sleeve to rotate said sleeve and the bobbin thereon, and said spur gear being of a material of relatively low wear resistance relative to that of said respective spiral face gear whereby said lower portion of said spur gear may wear away during use without any substantial wearing away of said respective spiral face gear, and whereby said spur gear may be removed from said sleeve, turned end-for-end and reinstalled on said sleeve to present a non-worn portion of said spur gear for engagement by said respective spiral face gear to inCrease the useful life of both the spur gear and the respective spiral face gear.
 10. A structure according to claim 9, wherein said spur gear is made from nylon (long-chain polymeric amide).
 11. A structure according to claim 9, wherein said spiral face gear is metal and said spur gear is plastic.
 12. A structure according to claim 11, wherein said plastic is nylon, thus obviating the need for a lubricant between said spur gear and said spiral gear. 